This reverts commit 749a58ab26.
This maintains feature parity with the autotools build. To achieve the
equivalent of --with-included-immodules=wayland,
-Dbuiltin_immodules=wayland,waylandgtk can be used instead.
Make it a yes/no/auto combo. "yes" means all modules are built into libgtk,
"no" that none are and "auto" uses the platform defaults, yes on win32,
no otherwise.
If we need more we can always extend it later.
Build the input modules for GTK+, either as modules or built directly
into GTK. Also provide a configure option to build the specified
immodules, or all, or the backend immodule(s) or none of the immodules
into GTK. Note that for Visual Studio all immodules are built into
the GTK DLL by default, like what is done in the Visual Studio projects.
Note that building the backend immodules for Quartz, X11 and Wayland are
currently untested.
